Xu Qiyu, Zhang Xingjian, Zhao Ruifeng, Li Shengjun, Liesche Johannes
Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101 Qingdao, China.
Shandong Energy Institute, 266101 Qingdao, China.
Plant Physiol. 2025 Feb 7;197(2). doi: 10.1093/plphys/kiaf015.
Understanding the molecular mechanisms of abiotic stress responses in plants is instrumental for the development of climate-resilient crops. Key factors in abiotic stress responses, such as the proton-pumping pyrophosphatase (AVP1), have been identified, but their function and regulation remain elusive. Here, we explored the post-translational regulation of AVP1 by the ubiquitin-conjugating enzyme UBC34 and its relevance in the salt stress and phosphate starvation responses of Arabidopsis (Arabidopsis thaliana). Through in vitro and in vivo assays, we established that UBC34 interacts with and ubiquitylates AVP1. Mutant lines in which UBC34 was downregulated showed higher tolerance to salt and low inorganic phosphate (Pi) stresses, while we observed the opposite for plants overexpressing UBC34. Our results showed that UBC34 co-localizes with AVP1, and AVP1 activity is enhanced in the plasma membrane fractions of ubc34 mutants, indicating that UBC34 mediates the turnover of plasma membrane-localized AVP1. We also observed that UBC34 affects the apoplastic pH but not the vacuolar pH of root cells. Based on our results, we propose a mechanistic model in which UBC34 mediates AVP1 turnover at the plasma membrane of root epidermal cells. Downregulation of UBC34 under salt and phosphate starvation conditions enhances AVP1 activity, leading to a higher proton gradient available for sodium sequestration and phosphate uptake.
了解植物非生物胁迫反应的分子机制有助于培育适应气候变化的作物。非生物胁迫反应中的关键因素，如质子泵焦磷酸酶（AVP1）已被确定，但其功能和调控机制仍不清楚。在这里，我们探讨了泛素结合酶UBC34对AVP1的翻译后调控及其在拟南芥盐胁迫和磷饥饿反应中的相关性。通过体外和体内试验，我们确定UBC34与AVP1相互作用并使其泛素化。UBC34表达下调的突变株对盐和低无机磷（Pi）胁迫表现出更高的耐受性，而对于过表达UBC34的植物，我们观察到相反的情况。我们的结果表明，UBC34与AVP1共定位，并且在ubc34突变体的质膜组分中AVP1活性增强，这表明UBC34介导质膜定位的AVP1的周转。我们还观察到UBC34影响根细胞的质外体pH，但不影响液泡pH。基于我们的结果，我们提出了一个机制模型，其中UBC34在根表皮细胞质膜中介导AVP1的周转。在盐和磷饥饿条件下UBC34的下调增强了AVP1活性，导致更高的质子梯度可用于钠隔离和磷吸收。
